Method for manufacturing high-temperature-resistant polyvinyl-chloride adhesive tape

ABSTRACT

The present invention relates to a method for manufacturing a high temperature-resistant polyvinyl chloride adhesive tape, and more particularly to a method and a production process for manufacturing a high temperature-resistant adhesive tape by applying a UV-crosslinkable hot-melt pressure-sensitive adhesive to a high temperature-resistant polyvinyl chloride film. The high temperature-resistant polyvinyl chloride film is a high temperature-resistant material containing a liquid polymeric plasticizer, a solid polymeric plasticizer, and a heat stabilizer. The hot-melt pressure-sensitive adhesive can be directly coated onto the high temperature-resistant polyvinyl chloride film at 130-150° C.; and then crosslinked and cured by UV irradiation, to make a high temperature-resistant polyvinyl chloride adhesive tape. Compared with conventional polyvinyl chloride adhesive tapes, the high temperature-resistant polyvinyl chloride adhesive tape manufactured using the method for manufacturing a novel high temperature-resistant polyvinyl chloride adhesive tape provided in the present invention has the advantages of non-volatility and resistance to high temperature and is highly environmentally friendly.

TECHNICAL FIELD

The present invention relates to the field of chemical technologies andchemical industry, particularly to a method for manufacturing a hightemperature-resistant polyvinyl chloride adhesive tape, and moreparticularly to a method and a production process for manufacturing anadhesive tape by applying a UV-crosslinkable hot-melt pressure-sensitiveadhesive to a high temperature-resistant polyvinyl chloride film. Thehigh temperature-resistant polyvinyl chloride film is a hightemperature-resistant material containing a liquid polymericplasticizer, a solid polymeric plasticizer, and a heat stabilizer. Thehot-melt pressure-sensitive adhesive can be directly coated onto thehigh temperature-resistant polyvinyl chloride film at 130-150° C.; andthen crosslinked by UV irradiation, to make a polyvinyl chlorideadhesive tape.

BACKGROUND ART

The electrical pressure-sensitive adhesive tape having a soft polyvinylchloride (SPVC) film as a substrate is widely used in automobiles,machinery manufacturing, instruments and household appliances because ofits excellent mechanical properties, flame retardancy, electricalinsulation properties, heat deformation resistance and superiorprocessability. However, the polyvinyl chloride film substrate containslow-molecular weight plasticizers such as dioctyl phthalate (DOP),dibutyl phthalate (DBP) and tri-n-butyl phosphate (TBP), etc. and haspoor temperature resistance. Moreover, these low-molecular weightplasticizers may migrate into the adhesive layer and decrease theadhesion powder of the adhesive tape, thus failing to meet therequirements in industrial application. The conventional polymericpolyvinyl chloride improves the high-temperature resistance, but cannotbe coated at temperatures above 120° C.

At present, the soft polyvinyl chloride adhesive tape products in theindustry are produced by directly coating a solvent-type rubber-basedpressure-sensitive adhesive on a soft polyvinyl chloride film. Thesolvent-type rubber-based pressure-sensitive adhesive contains a largeamount of organic solvent, generally toluene. During the coatingprocess, the organic solvent may be partially volatilized into theatmosphere to cause environmental pollution. The obtained polyvinylchloride adhesive tape also contains solvent residues, which will beslowly released during use and cause the pollution of the environment ofuse, such as the indoor environment of an automobile, thus failing tomeet the requirements of Restriction of Hazardous Substances Directive(RoHS Directive) in electrical and electronic equipment issued byEuropean Commission. Moreover, the coating process of the solvent-typerubber-based pressure-sensitive adhesive has the disadvantages of highenergy consumption, large floor area occupied by the coating equipment,and thus high production cost.

The UV-crosslinked hot-melt pressure-sensitive adhesive isenvironmentally friendly, and requires small equipment, low energyconsumption, and thus low production cost. More importantly, such apressure-sensitive adhesive has better plasticizer resistance, and themigration of polymeric plasticizers does not significantly decrease theperformance of the adhesive tape. Therefore, this type of hot-meltpressure-sensitive adhesives can meet a wide range of needs in theindustry. However, the polyvinyl chloride film plasticized with alow-molecular weight plasticizer and a conventional polymericplasticizer has insufficient temperature resistance. In order to preventthermal damage of the polyvinyl chloride film during coating, thetemperature at the time of coating has to be lowered, and an ultravioletlamp having a lower energy is used. When the coating temperature islowered, the viscosity of the adhesive is increased, and the flowabilityis deteriorated, which leads to an uneven coating. This limits the speedof coating and reduces the production efficiency. The applicantdescribed the use of an emulsion-type pressure-sensitive adhesive on apolyvinyl chloride film in Chinese Invention Patent No. CN 101372607 B,but the adhesive still needs to be further improved in terms of thehigh-temperature resistance.

SUMMARY OF THE INVENTION

In order to solve the above problems existing in the prior art, thepresent invention provides a method for manufacturing a novel hightemperature-resistant polyvinyl chloride adhesive tape. TheUV-crosslinked hot-melt adhesive has better high-temperature resistance.The method comprises: directly coating a UV-crosslinkable hot-meltpressure-sensitive adhesive onto a high temperature-resistant polyvinylchloride film substrate at a temperature of 130-150° C., and thencrosslinking by UV irradiation to make a novel hightemperature-resistant polyvinyl chloride adhesive tape.

According to the present invention, a method for manufacturing a hightemperature-resistant polyvinyl chloride adhesive tape is provided,which comprises:

coating, as a hot melt, a UV-crosslinkable hot-melt pressure-sensitiveadhesive onto a high temperature-resistant polyvinyl chloride film at atemperature of 130-150° C., and then crosslinking by UV irradiation witha set of UV lamps, wherein the high temperature-resistant polyvinylchloride film comprises a liquid polymeric plasticizer, a solidpolymeric plasticizer, and a heat stabilizer.

Further, the high temperature-resistant polyvinyl chloride film isprotected by cooling during the coating process to prevent the hightemperature-resistant polyvinyl chloride film from being damaged duringcoating and upon UV irradiation.

Optionally, the UV-crosslinkable hot-melt pressure-sensitive adhesivecomprises a copolymer of one or more polymerizable photoinitiators andan acrylate monomer, or a mixture of an oligomer containing one or morepolymerizable photoinitiators and an acrylate polymer, wherein theacrylate refers to all kinds of acrylate esters, for example, n-butylacrylate (BA), methyl methacrylate (MMA) and the like.

Further, the UV-crosslinkable hot-melt pressure-sensitive adhesive alsocontains a heat stabilizer, a photostabilizer, a tackifying resin, and aplasticizer.

Optionally, the liquid polymeric plasticizer is at least one selectedfrom the group consisting of liquid polyethylene glycol adipate andliquid polypropylene glycol adipate.

Optionally, the solid polymeric plasticizer is at least one selectedfrom the group consisting of an ethylene-vinyl acetate copolymer, anethylene-methyl acrylate copolymer, an ethylene-ethyl acrylatecopolymer, an ethylene-butyl acrylate copolymer, a nitrile butadienerubber powder, and chlorinated polyethylene.

Optionally, the heat stabilizer is at least one selected from the groupconsisting of a non-lead liquid or a solid barium/zinc stabilizer, acadmium/barium/zinc stabilizer, a calcium/zinc stabilizer, and anorganotin stabilizer.

Optionally, the polymerizable photoinitiator is an acetophenone orbenzophenone derivative containing a methacryloyloxy group or anacryloyloxy group.

Optionally, the amount coated of the UV-crosslinkable hot-meltpressure-sensitive adhesive in hot melt coating is 10-35 g/cm².

Optionally, the UV lamp is a high-pressure mercury lamp, a medium-to-lowpressure mercury lamp or an LED lamp, having a UV irradiation energy ofat least 10 mJ/cm².

Further, the coating is carried out by means of slot-die coating, barcoating or extrusion laminating.

In the method for manufacturing a novel high temperature-resistantpolyvinyl chloride adhesive tape provided in the present invention, ahigh temperature-resistant polyvinyl chloride film is used as asubstrate. In addition to the main polyvinyl chloride resin, the hightemperature-resistant polyvinyl chloride film also contains a liquidpolymeric plasticizer, a solid polymeric plasticizer and a heatstabilizer. The liquid polymeric plasticizer used in the presentinvention is a liquid polyethylene glycol adipate plasticizer and aliquid polypropylene glycol adipate plasticizer. The solid polymericplasticizer used is an ethylene-vinyl acetate (EVA) copolymer, anethylene-methyl acrylate (EMA) copolymer, an ethylene-ethyl acrylate(EEA) copolymer, an ethylene-butyl acrylate (EBA) copolymer, a nitrilebutadiene rubber (NBR) powder, and chlorinated polyethylene (CPE), etc.The heat stabilizer used is a non-lead liquid or a solid barium/zincstabilizer, a cadmium/barium/zinc stabilizer, a calcium/zinc stabilizer,or an organotin stabilizer. In addition, some colorants and fillers arefurther used as needed.

The use of the high temperature-resistant polyvinyl chloride filmsubstrate can increase the hot melt coating temperature for the adhesivetape to 150° C., thereby speeding up the coating and increasing theproduction efficiency. In addition, a polymeric plasticizer is added tothe polyvinyl chloride film to reduce the migration of the plasticizerin the film to the adhesive layer. That is to say, during the storageand use of the adhesive tape, or after baking at a high temperature of60-80° C., although the migration of a small amount of plasticizer fromthe substrate to the adhesive layer may occur, the performance of theadhesive tape can still be retained to meet the requirements forapplication in the industry. Therefore, the polyvinyl chloride adhesivetape produced using the production method of the present invention isenvironmentally friendly, and has high-temperature resistance, low VOC,and other excellent performances.

It is well known that the UV cross-linked hot-melt pressure-sensitiveadhesive does not contain a solvent, so a solvent recovery system is notrequired in the coating process, thus having the advantages ofenvironmental protection and energy saving. The hot-meltpressure-sensitive adhesive is commonly coated by slot-die coating, barcoating or extrusion laminating. Compared with a coating equipment forthe conventional aqueous and solvent-type pressure-sensitive adhesives,the coating equipment for the hot-melt pressure-sensitive adhesiveoccupies a small floor area and requires less labor for operation, andthereby the production efficiency can be greatly improved. The meltviscosity of the hot-melt pressure-sensitive adhesive is a veryimportant parameter, and the magnitude of the melt viscosity has adirect influence on the coating speed. At present, the rubber-basedhot-melt pressure-sensitive adhesive used in the industry generally hasa relatively large melt viscosity. When a soft polyvinyl chloride (SPVC)film is coated to manufacture a SPVC adhesive tape, a complicatedtransfer coating method has to be used (i.e., a method in which arelease paper is coated and dried, and then the adhesive layer istransferred to a SPVC film), and a simple direct coating method cannotbe used. Since during a direct coating process, in order to increase thecoating speed, it is necessary to raise the temperature of therubber-based hot-melt pressure-sensitive adhesive to 150° C. or more tolower the viscosity, so that coating can be carried out normally (themost common method). However, the increase in the temperature of theadhesive during coating will have many negative effects, such as thedestruction to substrates that cannot stand high temperature (especiallySPVC substrates) to cause thermal deformation or even thermaldegradation and also increased instability of the adhesive. TheUV-crosslinkable hot-melt pressure-sensitive adhesive used in thepresent invention has a lower melt viscosity than that of therubber-based hot-melt pressure-sensitive adhesive and can be directlycoated on a SPVC substrate at a low temperature (130-150° C.), withoutdestroying the soft polyvinyl chloride film substrate. In the presentinvention, the SPVC substrate is also cooled during the coating processto achieve the purpose of further protection.

The main component in known UV-crosslinkable hot-melt pressure-sensitiveadhesive is a mixture of acrylate monomers and their copolymers. Amongthe acrylate monomers, in addition to the commonly used n-butylacrylate, isooctyl acrylate, acrylic acid, methacrylic acid,hydroxyethyl acrylate, and hydroxypropyl acrylate, special monomers suchas methacrylamide, N-hydroxy methacrylamide, N-butoxyacrylamide, and(3-CEA, may also be used. Other special soft monomers, such as n-octylacrylate, dibutyl maleate, dioctyl maleate and norbornyl acrylate ormixtures thereof, may also be used sometimes. In order to increase theadhesion power, a tackifying resin such as a rosin resin, a terpeneresin, a petroleum resin or its corresponding hydrogenated or esterifiedmodified resin or the like may be used. In order to prevent the aging ofthe adhesive, an appropriate amount of an antioxidant is usually added.The UV-crosslinkable hot-melt pressure-sensitive adhesive needs tofurther contain one or more photoinitiators. The most commonly usedphotoinitiators include derivatives of acetophenone and benzophenone.The photoinitiator generates a radical group under the irradiation ofultraviolet light, more specifically under the irradiation of UVC, tofurther polymerize the acrylate monomers in the adhesive and crosslinkthe acrylate polymers for curing.

In the composition of the UV-crosslinkable hot-melt pressure-sensitiveadhesive used in the present invention, in addition to the abovecomponents, a copolymer of one or more polymerizable photoinitiators andan acrylate monomer, or a mixture of an oligomer containing one or morepolymerizable photoinitiators and an acrylate polymer may be furthercontained. The polymerizable photoinitiator is an acetophenone orbenzophenone derivative containing a methacryloyloxy group or anacryloyloxy group, for example, 2-hydroxy-4-(methacryloyloxy)benzophenone. Therefore, the oligomer containing a polymerizablephotoinitiator can lower the viscosity of the hot-melt adhesive, therebyreducing the coating temperature to provide a better protection for thepolyvinyl chloride substrate. The use of a high molecular-weightphotoinitiator in the composition of the UV-crosslinkable hot-meltpressure-sensitive adhesive can further reduce the volatility of theadhesive layer, such that the adhesive tape can well meet therequirement of environmental protection.

The method for preparing a novel high temperature-resistant polyvinylchloride adhesive tape provided in the present invention is implementedby a hot melt coater in a slot-die coating, a bar coating or anextrusion laminating process. The high temperature-resistant polyvinylchloride film substrate is mounted on an unwinding roller and led to awinding roller. The temperature of the adhesive melting oven is set to130-140° C., the temperature of the coating head is set to 130-150° C.,and the ratio of the rotational speed of the adhesive pump to the speedof the main machine is adjusted according to the weight of the adhesiveto be applied. The winding tension and unwinding tension are set and acooling unit is started. The speed of the main machine is adjusted, andthe coating head is moved slowly close to the surface of the polyvinylchloride film. The adhesive pump is opened and the coating is initiated.The gap distance between the coating head and the substrate is adjusted,and the speed of the coater is adjusted for coating. In the presentinvention, the hot-melt adhesive is coated in an amount of 10-35 g/cm².The adhesive layer is cross-linked and cured by UV irradiation with aset of UV lamps. The UV lamp used in the present invention is ahigh-pressure mercury lamp, a medium-to-low pressure mercury lamp or anLED lamp, having a minimum UV irradiation energy reaching 10 mJ/cm². Thecrosslinked and cured adhesive tape is wound and cut to obtain the hightemperature-resistant polyvinyl chloride adhesive tape product. In orderto prevent the polyvinyl chloride film substrate from being damagedduring UV irradiation during the coating process, the polyvinyl chloridefilm should be protected by cooling. The cooling method adopted in thepresent invention may be water cooling or air cooling, or both watercooling and air cooling may be used at the same time.

Performance test: The prepared UV-crosslinkable hot-meltpressure-sensitive adhesive is coated as a hot melt to a polyvinylchloride film substrate having a thickness of 0.15 mm by the abovemethod, and a small roll of an electrical pressure-sensitive adhesivetape with an adhesive layer having a thickness of 20 μm is obtained.After aging at 60° C. for 8 hrs, the adhesion properties are testedaccording to the following criteria: 1) The peel strength at 180° istested according to the National Standard of the People's Republic ofChina GB/T 2792-1998; 2) The initial adhesion performance of theadhesive tape is tested according to the National Standard of thePeople's Republic of China GB/4852-1984; 3) The high-temperatureresistance level is evaluated according to VW60360 (LV312); and 4) Themaintenance of the adhesion power of the adhesive tape is testedaccording to the National Standard of the People's Republic of ChinaGB/T4581-1988.

DETAILED DESCRIPTION

The illustrative and comparative examples of the present invention aredescribed in detail below. The illustrative examples are provided formaking the present invention clearer to those skilled in the art andmaking the present invention implementable based on the descriptionherein. The specific examples are not intended to limit the presentinvention, and the scope of the present invention is defined by theappended claims.

In the examples and comparative examples provided in the presentinvention, the following polyvinyl chloride films are used respectively:

1. High temperature-resistant polyvinyl chloride film having acomposition comprising, in percent by weight:

SG-3 polyvinyl chloride resin 57.5%   Ethylene glycol adipateplasticizer 25% Ethylene-methacrylate-carbonyl polymer  4% Nitrilebutadiene rubber powder 1.5%  Liquid barium/zinc stabilizer  2% Calciumcarbonate 10%

The raw materials are mixed, and then mixed by a high-speed mixer,milled in an open mill at a high temperature, extruded by an extruder,and rolled at high temperature by a three-roll or a four-roll calenderto prepare a polyvinyl chloride film.

2. Polyvinyl chloride films containing a DOP plasticizer are generallyavailable from the market.

Example 1

An acrylate copolymer of n-butyl acrylate, isooctyl acrylate, methylacrylate, and acrylic acid with a copolymerizable photoinitiator wasapplied to the above-mentioned high temperature-resistant polyvinylchloride film through a process as described above to prepare apolyvinyl chloride adhesive tape. The coating temperature was 140° C.

Example 2

An acrylate copolymer of n-butyl acrylate and acrylic acid with acopolymerizable photoinitiator was applied to the above-mentioned hightemperature-resistant polyvinyl chloride film through a process asdescribed above, to prepare a polyvinyl chloride adhesive tape. Thecoating temperature was 140° C.

Example 3

A mixture comprising 20% of an oligomer of n-butyl acrylate and acrylicacid with a copolymerizable photoinitiator and 80% of an acrylatepolymer was applied to the above-mentioned high temperature-resistantpolyvinyl chloride film through a process as described above, to preparea polyvinyl chloride adhesive tape. The coating temperature was 130° C.

Comparative Example 1

If an acrylate copolymer of n-butyl acrylate, isooctyl acrylate, methylacrylate, and acrylic acid with a copolymerizable photoinitiator wasdirectly applied to a polyvinyl chloride film containing a DOPplasticizer, the film wound be destroyed. Therefore, in this comparativeexample, transfer coating was employed, that is, the acrylate copolymerwas coated onto a release paper first, and then transferred to apolyvinyl chloride film containing a DOP plasticizer. The coatingtemperature was 140° C.

Comparative Example 2

The polyvinyl chloride adhesive tape for use in wiring harness forautomobile currently used in the industry is Huaxia adhesive tape FC110(high temperature-resistant PVC adhesive tape for use in wiring harnessfor automobile, manufactured by Hebei Huaxia Enterprise Co., Ltd.). Theadhesive used is a solvent-type rubber-based system, and the polyvinylchloride film used is a high temperature-resistant polyvinyl chloridefilm.

Comparative Example 3

The polyvinyl chloride adhesive tape for use in wiring harness forautomobile currently used in the industry is Huaxia adhesive tape UD110(PVC adhesive tape for use in wiring harness for automobile,manufactured by Hebei Huaxia Enterprise Co., Ltd.). The adhesive used isa solvent-type rubber-based system, and the polyvinyl chloride film usedis a polyvinyl chloride film a containing a DOP plasticizer.

TABLE 1 Performance data of adhesive tapes manufactured ComparativeComparative Comparative Example 1 Example 2 Example 3 Example 1 Example2 Example 3 Peel strength at 1.3 1.7 1.5 Serious 1.5 1.2 180° from steel“adhesive plate, N/cm loss” occurs Initial adhesion 17 19 18 uponunrolling 16 16 power, number of of the ball adhesive tape, Maintenanceof 240 300 270 and various 200 180 adhesion power, performances min arefailed to be tested Temperature 125 125 125 — 105 80 resistance level, °C. Aging test at 60° C. No No No — No No for 8 hrs adhesive adhesiveadhesive adhesive adhesive loss loss loss loss loss occurs occurs occursoccurs occurs upon upon upon upon upon unrolling unrolling unrollingunrolling unrolling

From the performance data of Examples 1-3 in Table 1, it can be seenthat the UV-crosslinkable hot-melt pressure-sensitive adhesive cansignificantly improve the high-temperature resistance of the polyvinylchloride adhesive tape, reaching a temperature resistance level of 125°C. The adhesive tape prepared with a solvent-type rubber has ahigh-temperature resistance level of 105° C. (Comparative Example 2). Ascan be known from the test results of Comparative Examples 1 and 3,UV-crosslinkable hot-melt pressure-sensitive adhesive has a resistanceto low-molecular weight plasticizers that is not as good as that of thesolvent-type rubber. In general, the UV-crosslinkable hot-meltpressure-sensitive adhesive is suitable for application to a hightemperature-resistant polyvinyl chloride film containing a polymericplasticizer, and the manufactured adhesive tape meets the industrialapplication specifications. In addition, the adhesive tape has excellenthigh-temperature resistance, is suitable for the wrapping and bundlingof cable bundles, and especially suitable for the wrapping and bundlingof cable bundles in automobile bodies.

1. A method for manufacturing a high temperature-resistant polyvinylchloride adhesive tape, comprising: coating, as a hot melt, aUV-crosslinkable hot-melt pressure-sensitive adhesive onto a hightemperature-resistant polyvinyl chloride film at a temperature of130-150° C., and then crosslinking by UV irradiation with a set of UVlamps, wherein the high temperature-resistant polyvinyl chloride filmcomprises a liquid polymeric plasticizer, a solid polymeric plasticizer,and a heat stabilizer.
 2. The method for manufacturing a hightemperature-resistant polyvinyl chloride adhesive tape according toclaim 1, wherein the high temperature-resistant polyvinyl chloride filmis protected by cooling during the coating process.
 3. The method formanufacturing a high temperature-resistant polyvinyl chloride adhesivetape according to claim 1, wherein the UV-crosslinkable hot-meltpressure-sensitive adhesive comprises a copolymer of one or morepolymerizable photoinitiators and an acrylate monomer, or a mixture ofan oligomer containing one or more polymerizable photoinitiators and anacrylate polymer.
 4. The method for manufacturing a hightemperature-resistant polyvinyl chloride adhesive tape according toclaim 3, wherein the UV-crosslinkable hot-melt pressure-sensitiveadhesive further comprises a heat stabilizer, a photostabilizer, atackifying resin, and a plasticizer.
 5. The method for manufacturing ahigh temperature-resistant polyvinyl chloride adhesive tape according toclaim 1, wherein the liquid polymeric plasticizer is at least oneselected from the group consisting of liquid polyethylene glycol adipateand liquid polypropylene glycol adipate.
 6. The method for manufacturinga high temperature-resistant polyvinyl chloride adhesive tape accordingto claim 1, wherein the solid polymeric plasticizer is at least oneselected from the group consisting of an ethylene-vinyl acetatecopolymer, an ethylene-methyl acrylate copolymer, an ethylene-ethylacrylate copolymer, an ethylene-butyl acrylate copolymer, a nitrilebutadiene rubber powder, and chlorinated polyethylene.
 7. The method formanufacturing a high temperature-resistant polyvinyl chloride adhesivetape according to claim 1, wherein the heat stabilizer is at least oneselected from the group consisting of a non-lead liquid or a solidbarium/zinc stabilizer, a cadmium/barium/zinc stabilizer, a calcium/zincstabilizer, and an organotin stabilizer.
 8. The method for manufacturinga high temperature-resistant polyvinyl chloride adhesive tape accordingto claim 3, wherein the polymerizable photoinitiator is an acetophenoneor benzophenone derivative containing a methacryloyloxy group or anacryloyloxy group.
 9. The method for manufacturing a hightemperature-resistant polyvinyl chloride adhesive tape according toclaim 1, wherein the amount coated of the UV-crosslinkable hot-meltpressure-sensitive adhesive in hot melt coating is 10-35 g/cm².
 10. Themethod for manufacturing a high temperature-resistant polyvinyl chlorideadhesive tape according to claim 1, wherein the UV lamp is ahigh-pressure mercury lamp, a medium-to-low pressure mercury lamp or anLED lamp, having a UV irradiation energy of at least 10 mJ/cm².
 11. Themethod for manufacturing a high temperature-resistant polyvinyl chlorideadhesive tape according to claim 1, wherein the coating is carried outby means of slot-die coating, bar coating or extrusion laminating.